In accompaniment with complexity of an information system that uses a network, it has become more and more difficult to specify a failure point when a communication failure or a communication quality degradation has occurred. For the sake of a quick recovery from a quality degradation (QoS degradation), a technique that can estimate a quality degradation point (point of QoS degradation) at a high precision is desired.
Conventionally, in order to estimate a quality degradation point in the network, for example, the quality of a flow (user flow) in the network is measured. Instead, a test communication (hereinafter, to be referred to as “a test flow) is performed in the network, and the quality of the test flow is measured. Here, the flow is a flow of packets between terminals in a certain application. The quality degradation point can be estimated in accordance with the quality of a flow passing through various routes. In order to improve the estimation precision of the quality degradation point, the selection of a route for the test flow is important.
In “Estimating points of QoS degradation in the network from the aggregation of per-flow quality information” (The Institute of Electronics, Information and Communication Engineers, TM Research Group, Vol. 104, No. 707, Pp. 31-36, May 3, 2005) by Masayoshi Kobayashi, Yohei Hasegawa, and Tsutomu Murase, a method of estimating a quality degradation point is disclosed. According to this method, the quality degradation point is estimated by using both of the quality of a user flow and the quality of a test flow in a network. Specifically, a group of test flows is determined such that the test flows pass through links included in a set of links through which the user flow passes. Here, the test flow set, namely, test flow routes are determined such that the links through which the respective test flows pass are different from each other. Measuring the quality degradation in the different test flow route allows the quality of each link to be determined to be degraded.
FIG. 1 is one example of a flow/link correspondence table that indicates a relation a plurality of test flows used in an estimating method and links to which the test flows are applied. A set of links to which the user flows are applied includes links L0 to L3. The links to which respective test flows are applied are different from each other. Each test flow is configured to be applied to only a certain link and not to be applied to the other links. Since the plurality of test flows are used, the link whose quality is degraded is estimated. However, this method requires to search the test flow which passes through only a targeted link. The restriction to search the test flow is severe, and a probability at which the test flow can be discovered is low. When the test flow that passes through only one link cannot be generated, the link in which the quality degradation occurs cannot be detected. Moreover, the search for the routing is required at each node or terminal that serves as the end point of each link. Thus, the search cost becomes expensive.
As other techniques related to control of a communication route, the followings are known.
Japanese Laid Open Patent Application (JP-P2002-64493A) describes a control method of a communication route in a plurality of networks. The plurality of networks are connected to each other and managed by a network managing system. Each network has a network apparatus. According to this control method, a communication conductivity of the route from a network apparatus in a first network to a network apparatus in a second network is held.
Japanese Laid Open Patent Application (JP-P2002-271392A) describes a voice quality managing method for each call in an IP network. A telephone communication quality for each call is monitored from a remote end. A quality degradation is detected in substantially real time. Since the measurement is performed without any installation of an external measuring apparatus, a cost is suppressed. Also, delay information in end-to-end is collected.
Japanese Laid Open Patent Application (JP-P2003-258903A) discloses a communication path monitoring system. The communication path monitoring system monitors a communication path established between data processors, in the communication network composed of a plurality of data processors and propagation paths. In particular, the communication monitoring system contains an attribute value obtaining unit for obtaining an attribute value of a communication path as a monitor target. The attribute obtaining unit has first to third units. The first unit obtains control information to establish the communication path that serves as the information transferred between the data processors. The second unit extracts the setting information with regard to the obtainment of the attribute value, from the obtained control information. The third unit uses extracted setting information and obtains the attribute value from the information that passes on the established communication path.